The D-Link DNS-323 is a bargain-priced, consumer-grade network storage enclosure, similar to countless others. It's made of cheap plastic, has uninspired design, and a clunky web-based management interface. It's also brilliant, and if you have any hacker in you at all, you should buy one.

Building your own NAS is not very rewarding. Either you do it the easy way or the hard way. The easy way is just buying cheap hardware, slapping it together and configuring. Time consuming and pretty cheap, but you'll probably wind up consuming far more power than an off the shelf NAS. The hard way would be to do your due diligence, get the right components and build something that's about the same as what you could get in an off the shelf NAS (minus the molded plastic, maybe) but by now you've spent more than you would have on the OTS device.

Bottom line: Don't do it if you need a NAS, do it if you love doing stuff like this and need a NAS.